Why does Linda Brent have a relationship with Mr. Sands?

Flint has been making sexual advances toward Linda for a very long time, and threatens to move her to another location where she will not be protected by the presence of her family. Thus, Linda chooses to have a relationship with Mr. Sands, hoping to prevent Flint from going through with his plan. When Flint tells her the time has come to move into the house he has specially prepared for her..... Linda tells him she is pregnant. Flint is enraged.